Numerical modeling of seepage and deformation of unsaturated slope subjected to post-earthquake rainfall

Slope is susceptible to rainfall-induced failure after being damaged by earthquake. In this study, the seepage and deformation of unsaturated slope during post-earthquake rainfall were investigated using the finite element method. Shaking-induced plastic modulus reduction dependent on deviatoric strain and shaking-induced permeability change dependent on volumetric strain were considered in the modeling of slope response to the following rainfall; the damage concept was adopted to describe shaking-induced cracks and assess the impact of surface cracks on permeability enhancement and strength reduction. Then, numerical modeling of the hydro-mechanical response of slope to rainfall was performed with the updated model. Analysis showed that earthquake significantly affected the slip surface of slope subjected to the following rainfall since soil with reduced shear modulus further deformed, causing a more severe landslide, whereas the influence of earthquake-induced permeability reduction was not great; earthquake-induced damage should be incorporated in the analysis of slope response to rainfall since it altered landslide characteristics. Analysis was generally consistent with centrifuge experiments based on the discussions of pore water pressure, stress path, slope deformation, and soil displacement in simulations and experiments. The coupled hydro-mechanical analysis with the proposed modeling methods could evaluate the response of unsaturated slope to post-earthquake rainfall.